This is really two books in one, which may be why it is rather long. "Pinker One" lays out convincingly the reasons why we cannot possibly do without a concept of human nature. He knows why people have found that concept threatening. He knows it has often been used to justify oppression. But he explains carefully and sensitively why this misuse is no part of the concept itself - why the moral consequences that have been drawn from ideas of human nature did not follow from the facts used to support them.

Attacking the linked doctrines of empiricism ("the blank slate"), romanticism ("the noble savage") and dualism ("the ghost in the machine"), he urges us to accept realistically, in our theories as we do in everyday life, that much of our conduct and feelings are indeed rooted in the physical nature that is given to us, rather than coming from a mysterious entity called society or appearing from nowhere. That nature is, he says, a rich and legitimate heritage, not an extraneous tyrant.

All this is surely fine; indeed I have said much of it myself. The trouble begins when "Pinker Two" starts to tell us how to understand this nature, now that we can believe in it again. He offers just three lifelines: the "new sciences of the mind", cognitive science, behavioural genetics and evolutionary psychology. These, he says, have freed us from our age-long ignorance.

"Beginning in the 1950s, with the cognitive revolution, all that changed. It is now possible to make sense of mental processes, and even to study them in the lab... Before the revolution, commentators invoked enormous black boxes such as 'the intellect' or 'the understanding', and they made sweeping pronouncements about human nature, such as that we are essentially noble or essentially nasty. But we now know that the mind is not a homogeneous orb invested with unitary powers or across-the-board traits. The mind is modular... In the study of humans, there are major spheres of human experience - beauty, motherhood, kinship, morality, co-operation, sexuality, violence - in which evolutionary psychology provides the only coherent theory and has spawned vibrant new areas of empirical research... The mental world can be grounded in the physical world by the concepts of information, computation and feedback... Thinking is a physical process... We are our brains..."

If that is what we are, some people might wonder what has happened to the rest of our bodies? But the trouble goes deeper. "Pinker Two" relies heavily on a sharp, dramatic contrast between "science" and the rest of thought. He sees his favoured doctrines as science - respectable, ordered thinking, the only right way to go. He offers them as the only proven theories, contrasted with primitive, disorganised "intuition" which is all anybody has used until now. He reports their views as factual discoveries.

But cognitive science and evolutionary psychology are not physical sciences that could make this sort of claim. Their conclusions are not discoveries that can be reported objectively without involving conceptual changes. Though they use data from more detailed sciences, they are themselves parts of social science - particular interpretative schemes using new selections from the data, new ways of viewing familiar facts. These patterns can bring out different features of a complex whole. But they do not supersede their predecessors. They complement them.

The claim to scientific status has, of course, repeatedly been made for such patterns during the last century. Since behaviourism patented the method, aspiring new ideologies have taken care to appear in scientific dress, using apparatus drawn from the physical sciences and claiming their authority. (Even creationism now appears as creation science.) But if these theories reach the general public, what really matters in them is their principles of selection - the ideas that determined their special approach in the first place. At this level, the most effective factor is often the imagery.

The case of behavioural genetics is interesting. Genetics is, of course, indeed a physical science. But applying it to human behaviour is a complex business that involves huge problems of selection. Different ways of classifying behaviour express different attitudes, suggesting dramatically different conclusions, so these attitudes are crucial.

The reason why "the gene" has now become a household word is not that we have all suddenly begun to understand genetics. We haven't. What has brought the word to public notice is the metaphor linked with it - selfishness - a metaphor that seemingly claimed to resolve long-standing debates about motivation. It appeared to show that Hobbes and Herbert Spencer were right after all. Self-interest was indeed the only effective human motive.

Of course the word officially has only a technical meaning, describing the reproductive effect of a gene. Pinker writes it off as just a casual figure of speech. But so lurid and controversial a term cannot possibly be cleansed of its everyday meaning. People who are clear about what they are saying avoid using such metaphors in the first place. Unmistakably, this imagery has often actually misled the fathers of sociobiology themselves, since they regularly and cheerfully describe the motivation of people - not that of genes - by phrases such as "we are selfish".

The effect of this ambiguity has been to bring back many of the dreary ideas that had earlier discredited the notion of human nature, notably the social-Darwinist reliance on self-interest, attaching them firmly in the public mind to genetic science. The uncritical use of economic and political metaphors like investment, manipulation and war-games has deepened this effect, making it very hard for this whole line of thought to bring back the notion of human nature into good repute, as "Pinker One" hopes.

Neither, unfortunately, will the ambiguous and muddled notion of "information" serve to fulfil his other hope of mending the mind-body gap. To do that, we will have to dig a lot deeper and understand what has made us let them drift apart in the first place.

What, however, about evolutionary psychology? Here again the basic insight is surely sound. Our emotional nature is indeed not a neat system but a roughly evolved balance, producing conflicts and confusions that cause us endless trouble. Moreover, we now live in crowded, artefact-filled conditions very different from those that prevailed when it was formed, which may well subject it to extra strains. As "Pinker One" rightly says, this is a tragic predicament and should be taken seriously.

But how to deal with it? Evolutionary psychology proposes that we should discover the details of our nature, first by inferring them from the social conditions that prevailed when it was formed in the Stone Age, and, second, by atomising it, dividing it into separate "modules" that determine distinct particles of behaviour.

Despite Pinker, these are desperate strategies that have produced very few results of any interest. The first method fails because we don't know any Stone Age sociology. (Any moderately persuasive stories that EP has produced owe their plausibility to data from other sources.) The second is mistaken because minds work as a whole and no amount of splitting will reveal their general structure. However gravely we need a notion of human nature, this isn't the way in which we are going to find it.